<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            background-color: skyblue;
            padding: 20px;
            display: flex;
            width: 500px;
            height: 500px;
            justify-content: space-between;
        }
        .item-1 {
            width: 20px;
            height: 20px;
            background-color: lightgreen;
        }
        .item-2{
            width: 20px;
            height: 20px;
            align-self: center;
            background-color: lawngreen;
        }
        .item-3{
            width: 20px;
            height: 20px;
            align-self: flex-end;
            background-color: lightcoral;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="item-1"></div>
        <div class="item-2"></div>
        <div class="item-3"></div>
    </div>
</body>

</html>